N = int(input())
A = list(map(int,input().split()))

l = []
l.append(1)
for i in range(1,N):
    if A[i] == A[i-1]:
        l[-1] += 1
    else:
        l.append(1)
n = len(l)
dp = [[0] * 2 for _ in range(n)]
dp[0][1] = l[0]
for i in range(1,n):
    dp[i][0] = max(dp[i-1][1],dp[i-1][0])
    dp[i][1] = dp[i-1][0] + l[i]
print(max(dp[-1]))